But what are the actual rules of capitalization? And, in an era of tweeting, texting and Trump, when is it O.K. to break them? We talked to experts and channeled our inner nerds to bring you this handy guide.

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The president’s original tweet about capitalization, which he eventually deleted.

Why are we talking about capitalization?

Experts say overcapitalization can be traced to the 17th and 18th centuries, when it was common to uppercase many significant words.

In line with the times, the founding fathers used this style in the United States Constitution, said Kory Stamper, a lexicographer and the author of “Word by Word: The Secret Life of Dictionaries.”

Over the past several years, Ms. Stamper said, she has noticed that some people with conservative viewpoints have increasingly used frequent capitalization. “There is definitely a heavy tie to wanting to mimic the founding fathers, and they seem to have latched on to capitalization as the way to do it,” she said.

When should I use capitalization?

Most people know that you should capitalize the first word in a sentence, the pronoun “I” and proper nouns.

There are other times when capitalization is needed, but, even at this basic level, things can start to get tricky.

“The confusion tends to be around what’s considered a proper noun and what’s not,” Ms. Stamper said. “Is ‘earth’ a proper noun? When do you capitalize titles and honorifics like ‘president’ or ‘prime minister’?”

What is a proper noun?

Dictionary.com defines a proper noun as the name of a specific person (Beyoncé), place (Paris), company or institution (The New York Times) or thing (Golden Gate Bridge).

Ms. Stamper said it is a common mistake to universally apply capitalization to words such as “earth” and “moon.”

O.K., but really: Is it kosher to capitalize for emphasis?

It depends, said Bryan A. Garner, a grammarian who is the author of “Garner’s Modern English Usage.”

Some acclaimed writers, such as David Foster Wallace, have used capitalization for emphasis in a way that many consider literary, he said. But, he said, the rules are there for a reason — and you have to know them in order to break them.

“If you want to come across as a literate writer, you should adhere to those standards,” he said. “But if you don’t care about how you look to others, then you just capitalize according to your own feelings.”

So if not capitalization, then what?

Use italics, Mr. Garner said. If you are tweeting or texting, he said, you can use asterisks on either side of the word for *emphasis*.

Should I capitalize every word in a sentence?

Only if You Want to Be Annoying.

Or if You Write Headlines for a Certain Newspaper.

And in that case, Mr. Garner said, some words should still remain lowercase, including: articles (a, an, the); conjunctions (and, or, but) and prepositions with fewer than four letters (of, by, to, for).

Should I capitalize the ‘g’ in God?

Don’t get Twitter started on this one.

Personal religious views aside, experts say it depends on which kind of god you are referring to.

“It used to be when I was a kid that yes, anytime you use the word ‘God’ you capitalized it,” Ms. Stamper said. “Now it tends to be only if you are referring to the Abrahamic God.”

Am I a grammar expert now?

If you made it this far, you get an A for effort.

But Mr. Trump’s tweet had grammar geeks abuzz about more than just capitalization. “Everybody is picking up on the dangling modifier and the incorrect ‘pour,’” Ms. Stamper said.